This invention relates to high-speed precision positioning apparatuses useful for processing of devices such as semiconducting wafers, for micro-scale experimentation, or for high resolution electron microscopy of biological or other samples.
Semiconductor processing equipment often requires high-precision positioning of a silicon wafer. Large-size wafers with very small features often require high-precision positioning combined with a large range motion of the wafer stage that supports the wafer.
In addition to high precision and a large range motion, high-speed scanning is useful for achieving high manufacturing throughput.
A typical example of semiconductor processing equipment is a laser used in microlithography. Certain traditional systems for semiconductor laser processing include a translation stage that can support the wafer and move it under a fixed laser beam. The wafer-supporting translation stage may move along the X or Y directions, for example.
In certain processing equipment a linear motor and a bearing system are used to move the wafer-supporting stage along a rail in the X-direction. To move the wafer-supporting stage in the Y-direction an intermediate rail is used that carries the rail and the wafer-supporting stage in the Y-direction while allowing the wafer-supporting stage to slide along the rail in the X-direction.
In addition to drive motors, various moving parts, bearings, and wafer, the wafer-supporting stage may carry a position detector. The position detector may be a laser-distance interferometer that is usually heavy, and requires environmental shielding of the optical path and slow motion in order to achieve high accuracy readings.
Hollis, U.S. Pat. No. 5,153,494, describes an apparatus capable of moving light loads in X, Y, and yaw (rotation around the Z axis) in limited range and with high speed. Vibrations of the stationary portions of the apparatus are reduced by a momentum-canceling design. The momentum canceling design includes, in addition to the movable wafer-supporting stage, a non-coplanar moving element that moves in a momentum canceling manner with respect to the movable wafer-supporting stage. The motors include fixed permanent magnets and coils that are attached to the wafer-supporting stage and move along with the wafer-supporting stage.
Trumper, U.S. Pat. No. 5,196,745, describes an apparatus capable of providing movement in the 200 to 300 mm range in one or two degrees of freedom and having precision control in the 10 nm range in the remaining degrees of freedom. Linear motion of the wafer-supporting stage is provided by a motor having an array of permanent magnets attached to the movable wafer-supporting stage and a fixed array of commutating coils attached to the stator. The commutating coils have coupled magnetic flux lines. Current is allowed to flow only in those sections of the array where the motion takes place, in order to reduce energy losses in the coils. The motion is facilitated by magnetic bearings.